Efficacy Study of Vortioxetine (Lu AA21004) in Adults With Major Depressive Disorder

Inclusion Criteria: * Has a primary diagnosis of major depressive episode according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) criteria. * The reported duration of the current major depressive episode is at least 3 months. * Has a Montgomery Åsberg Depression Rating Scale (MADRS) total score ≥26. * A male or a female of childbearing potential who is sexually active agrees to use adequate contraception from Screening throughout the duration of the study and for 1 month after the last dose of study medication. Exclusion Criteria: * Has 1 or more the following: * Any current psychiatric disorder other than major depressive disorder as defined in the DSM-IV-TR. * Current or past history of: manic or hypomanic episode, schizophrenia or any other psychotic disorder, including major depression with psychotic features, mental retardation, organic mental disorders, or mental disorders due to a general medical condition as defined in the DSM-IV-TR. * Any substance disorder (except nicotine and caffeine) within the previous 6 months as defined in the DSM-IV-TR. (must have negative urine drug screen prior to Baseline). * Presence or history of a clinically significant neurological disorder (including epilepsy). * Neurodegenerative disorder (Alzheimer disease, Parkinson disease, multiple sclerosis, Huntington disease, etc). * Has a significant risk of suicide according to the investigator's opinion or has a score ≥…